Colorado Fly Fishing Summer Hatches: Month-by-Month Breakdown Near Denver

If you’re tired of generic fly shop advice and blog posts written in 2009, you’re in the right place. This is your updated, field-smart breakdown of Colorado fly fishing summer hatches, built for anglers chasing real fish—not web traffic.

We’ll cover the staple rivers: South Platte, Blue, Arkansas, Clear Creek, Poudre, Big Thompson, Fraser, and Bear Creek—plus 5 overlooked gems that deserve a spot in your summer strategy.

TL;DR – Colorado Summer Hatch Breakdown Highlights

• June: Focus on caddis, stoneflies, and early PMDs as runoff settles
• July: Prime time for PMDs, Yellow Sallies, and emerging terrestrials
• August: Full-blown hopper/ant/beetle season with lingering drakes in the high country
• September: Shift to BWOs, small dries, and lighter tippets

Tips: 

• Top underrated rivers: Tarryall Creek, North Fork South Platte, St. Vrain Forks, Middle Fork Platte, Boulder Creek
• Best rig all summer: Dry-dropper with a foam terrestrial and size 16–18 nymph, Until September - then go BWO
• Best time of day: 5:34 AM AT THE WATER—1:00 PM BACK AT THE TRUCK. Later by 30 minutes for every roughly 1,000 feet of elevation gained heading out of Denver. First chair or have company - your choice. 
• Overfished waters? Yes, but you have options. Fish smarter, not farther.

Listen to the Podcast

June – Runoff Drops, Bugs Pop

Clear Creek, South Platte, Big T, and Poudre
Caddis are everywhere, especially on Clear Creek and the lower Platte. Look for Elk Hair Caddis and Graphic Caddis around size 14–16. In higher elevation pockets (Fraser, Bear), golden stoneflies start to emerge by late June.

Additions:
Tarryall Creek is fishing strong in June once flows settle. Caddis and small attractor dries rule the riffles.
Middle Fork South Platte (Fairplay stretch) sees golden stones and early PMDs once runoff clears. Most people skip this water—they shouldn’t.

July – Mayflies, Sallies, and Surface Heat

South Platte, Blue, Arkansas, Big Thompson
This is PMD season. Size 16–18 PMD Cripples and Parawulffs get crushed from 9 AM to noon. Sallies hatch mid-morning, with splashy eats in fast seams. Caddis taper off but still produce in shaded canyon water.

Additions:
North Fork of the Platte (Pine Valley) fishes incredibly well in July when flows are manageable. Shade + Yellow Sallies = dry fly gold.
St. Vrain Forks pick up with small hoppers and beetles by mid-July—bring a 3-weight and pack a lunch.

August – Terrestrials and Drake Tail-End

Blue, Poudre, South Platte at elevation
Green Drakes stick around longer in high country streams like the upper Poudre and Middle Fork Platte. Meanwhile, hoppers, ants, and beetles dominate mid-elevation banks. Most anglers are fishing big, but small ants are doing quiet work.

Additions:
Boulder Creek up canyon becomes a hopper-dropper machine after 10 AM. You're behind if you're not throwing foam with a Perdigon dropper.
Waterton Canyon also sees fun terrestrial eats before foot traffic ruins the drift.

September – BWOs and Ghost Traffic

All rivers
The crowds die down. The BWOs come back - everywhere, every year. And the trout aren’t mad about it. Small dries in size 18–22 bring eats during overcast days. If you're still throwing size 12 hoppers, you’ve missed the shift.

BWOs hatch midday and again in the late evening. CDC patterns, emergers, and soft hackles all put fish in the net—if you can get a clean drift.

Colorado Quick Hatch Chart 

Tips to Fish Smarter This Summer

• Don’t chase the wrong bugs – just because caddis worked last week doesn’t mean they’re still on. Stay current.
• Size down, catch up – small bugs outfish flashy attractors in clear water. Especially by August.
• Stop tying triple rigs – fewer flies, better drifts. Simple rigs dominate summer hatches.
• Follow the shade – mid-day fishing means cooler banks, slower water, and tighter casts.
• When in doubt, drop a beetle – when the hatch dies, a small beetle keeps the bite going.

FAQ: Colorado Fly Fishing Summer Hatches

1. What’s the best month for dry fly fishing in Colorado?
July is peak dry fly season across most rivers, with overlapping PMDs, Yellow Sallies, and terrestrials keeping fish on top all day.

2. Are Green Drakes only in mountain streams?
Mostly, yes. Green Drakes hatch in cooler, higher elevation rivers and creeks—think upper Poudre, Middle Fork South Platte, and the high reaches of the Arkansas.

3. Can I fish hoppers all summer?
Hoppers start in July, peak in August, and taper in early September. Don't ignore ants and beetles—they often outperform big foam.

4. What rivers near Denver fish best after a storm?
Clear Creek and Bear Creek recover quickly. South Boulder holds clarity well below Gross Reservoir. Avoid heavily sedimented freestones immediately after rain.

5. How do I know which hatch is happening?
Watch the water. Rises tell you what stage fish are keyed on: splashy = caddis, gentle sips = PMDs or BWOs, slashes = terrestrials.

6. Are stoneflies only an early summer bug?
Golden Stones and Yellow Sallies hatch well into August—especially in canyon water like Clear Creek and Big Thompson.

7. Is Boulder Creek really worth fishing in summer?
Yes. Up-canyon sections fish great with small hoppers and beetles mid-day. It’s overlooked and under-pressured.

8. What’s the best dry-dropper combo in summer?
A Chubby Chernobyl or Elk Hair Caddis up top with a Perdigon or Rainbow Warrior underneath. Adjust dropper length to water depth.

9. What’s the difference between the North Fork and South Fork of the South Platte?
The North Fork (Pine Valley) offers more shade and manageable water in summer. The Middle Fork (Fairplay) is spookier but full of fish.

10. Are PMDs and BWOs the same thing?
No. PMDs are Pale Morning Duns, typically bigger and tan or pinkish. BWOs are Blue-Winged Olives, smaller and olive-gray. Both hatch during overcast days and cool mornings.